I installed the NAPA kits and the cylinders held pressure perfectly. I tested them by installing them in a vise end-to-end, without the dust boots. The vise kept the pistons from popping out. I hooked a Motive pressure bleeder to them using a metal brake line screwed into the cylinder at one end, and clamped the other end (with fitting cut off) into the pressure bleeder hose. With bleeder screw opened and facing up, I applied low pressure until the cylinder filled, then closed the bleeder, then pumped pressure up to 15 psi, then let each cylinder sit for 1/2 hour under pressure to ensure there was no leakage.
